For example, Patent Document 1 discloses, as shown in FIG. 6A, junction (in another word joining) between the junction surface of an aluminum roof panel 1 and the junction surface of a steel side roof rail 2 by a rivet 4. A structure bonding agent 3 of electrical insulation is interposed between the respective junction surfaces of the aluminum roof panel 1 and the steel side roof rail 2.
Further, Patent Document 2 discloses, as shown in FIG. 6B, junction in which a hetero-material junction rivet (in other words, a different material joining rivet) 6 is made penetrate through and joined with a panel 5 formed from a steel material, and thereafter the hetero-material junction rivet 6 is spot welded to a panel 7 formed from an aluminum alloy material so that the hetero-material panels 5 and 7 are joined with each other.
Still further, Patent Document 3 discloses, as shown in FIG. 6C, a connection structure in which hetero-metal members 8a and 8b are at least partially in contact with each other, and in this state, a metal layer 9 straddling between the both material members 8a and 8b indirectly connects the hetero-metal members 8a and 8b. In Patent Document 3, it is described that the metal layer 9 is formed by a cold spray method or a warm spray method. Incidentally, unlike the structures described in Patent Documents 1 and 2, the connection structure disclosed by Patent Document 3 does not connect the boundary surfaces of hetero-metal members.